<template>
  <div class="scroll-container" ref="scrollContainer" @wheel.prevent="handleScroll">
    <div class="scroll-wrapper" ref="scrollWrapper" :style="{left: left + 'px'}">
      <slot></slot>
    </div>
  </div>
</template>

<script>
const padding = 15; // tag's padding

export default {
    name: 'scrollPane',
    data() {
        return {
            left: 0
        };
    },
    methods: {
        handleScroll(e) {
            const eventDelta = e.wheelDelta || -e.deltaY * 3;
            const $container = this.$refs.scrollContainer;
            const $containerWidth = $container.offsetWidth;
            const $wrapper = this.$refs.scrollWrapper;
            const $wrapperWidth = $wrapper.offsetWidth;

            if (eventDelta > 0) {
                this.left = Math.min(0, this.left + eventDelta);
            } else {
                if ($containerWidth - padding < $wrapperWidth) {
                    if (this.left < -($wrapperWidth - $containerWidth + padding)) {
                        this.left = this.left;
                    } else {
                        this.left = Math.max(this.left + eventDelta, $containerWidth - $wrapperWidth - padding);
                    }
                } else {
                    this.left = 0;
                }
            }
        },
        moveToTarget($target) {
            const $container = this.$refs.scrollContainer;
            const $containerWidth = $container.offsetWidth;
            const $targetLeft = $target.offsetLeft;
            const $targetWidth = $target.offsetWidth;

            if ($targetLeft < -this.left) {
                // tag in the left
                this.left = -$targetLeft + padding;
            } else if ($targetLeft + padding > -this.left && $targetLeft + $targetWidth < -this.left + $containerWidth - padding) {
                // tag in the current view
        // eslint-disable-line
            } else {
                // tag in the right
                this.left = -($targetLeft - ($containerWidth - $targetWidth) + padding);
            }
        }
    }
};
</script>

<style rel="stylesheet/scss" lang="scss" scoped>
.scroll-container {
  white-space: nowrap;
  position: relative;
  overflow: hidden;
  width: 100%;
  .scroll-wrapper {
    position: absolute;
  }
}
</style>
